A wireless power transmission or a wireless energy transfer refers to a technology of wirelessly transferring electric energy to desired devices. In the 1800's, an electric motor or a transformer employing the principle of electromagnetic induction has been extensively used and then a method for transmitting electrical energy by irradiating electromagnetic waves, such as radio waves or lasers, has been suggested. Actually, electrical toothbrushes or electrical razors, which are frequently used in daily life, are charged based on the principle of electromagnetic induction. The electromagnetic induction refers to a phenomenon in which a voltage is induced so that a current flows when a magnetic field is varied around a conductor. Although the commercialization of the electromagnetic induction technology has been rapidly progressed around small-size devices, the power transmission distance thereof is short.
Until now, the long-distance transmission using the electromagnetic induction, the resonance and the short-wavelength radio frequency has been used as the wireless energy transfer scheme.
Recently, an energy transfer scheme has been extensively used based on the electromagnetic induction or the resonance among wireless power transmission schemes.
According to the conventional energy transfers scheme based on the electromagnetic induction or the resonance, since a coil generally has a spiral structure or a helical structure, there is a limitation when increasing the power transmission efficiency.
As a related art, there is Korea Unexamined Patent Publication No. 10-2012-0116799.